Sound recording apparatus



May 31, 1932, D, A w-Hg-[SQN l 1,861,039.'

som nscRDxNG APPARATUS l y f filed nay 17, 192e 5 mes-Saget 1 FIE-1..

' mvsmon 96Wf4-mem i ms ATTORNEY A.. 1.. R 6 o. ..8 T. A. Wr. S u 1W m wnm su... mm1 n Iv wm ,Nm Amm om o S .um i.: 9 1 L. 3 v. a M

May 31, 1m M www; 1,861,039 '1Q-*4 f )SOUND assomme APPARATUS f Filed nay 17, '192.8 #s sheet'smmet 3 v i l U] ,l

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Fmi?

mmmmw lll' ms ATToRNgY UNiTeD STATES- PATEN'T 'o minima a. vvnrcison, or Los ANGELES, camroiamia, assrenon. ro wmrsorr encrornonn conrona'rron, or Los ANGELES, CALIFORNIA, A conrona'rron or Nnvana som nsconnnm manning. if I 'z 1.1;.; i .ippiicauon ned my' 17, 192s. sei-iai mi. 278.554.' I V .This invention relates to the recording of sound, especially by the aid of radiant energy affecting a sensitive medium.

It is now Well known that sound records can he produced on a member the liysical characteristics of which are affect by radiant energy, such as light, varying in accordance ivitli the sound to be recorded. For example, the density of a film can be thus affected, or the intensity of a light image or any forni of sensitive strip, u on running such a strip in connection wit an electric circuit thatresponds to light variations, electrical currents, varying in accordance with these variations .in density or intensity are produced; and these varying currents can affect a sound reproducer, such as a loud speaker.

In one scheme for recording sound waves, polarized light is used, the intensity of which is caused to vary in accordance with the sound waves to be recorded. This is accomplished bythe aid of a primary and a secondary polarizer, the planes of polarization of which are set at angles to each other; and

the rotation of polarized light passing between the two polarizers, is effected in accordance with the sound to lbe recorded. It

, is evident that the light which is permitted to pass through both polarizers de nds upon the relative angular positions' ofpilie plane of polarization of the light, and the plane of polarization of the secondary polarizer or analyzer. If these planes are parallel, a'

maximum transmission of light occurs; and

I if they are at right angles, the light is ex tinguished in the analyzer. Thus it is evident that variations in the relative angles of' these planes of polarization cause correspond ing variations in the amount of light trans mitted.

It is one of the objects of my invention toimprove in general the t of sound recording apparatus, which utilizes polarized'light in this manner.I

In prior schemes, the rotation of polarized y light has been affected by 4varying the intensity of a magnetic field through which the 1i ht must pass. However, I find that some-- w at better results can be obtained by using influence t ie polarized light; and it is acin such a way that'the effectiveness of the electric field is multiplied, and whereby a much larger degree of rotation for the po ized beam can lie-obtained than in other prior devices;

My invent-ion possesses many other advantages, and has other objects .which may be made more easily apparent from a consideration of several embodiments of -my invention. For this purpose I have shown a few forms in the drawings accompanying and forming part of the present specification. I shall now proceed to describe these forms in detail,. which illustrate the general principles of my invention; but it is to be under stood that this detailed description is not to be taken in a limiting sense since 'the scope of my invention is best defined by the ap-l Fig. 3 isa schematic diagram of another f form of my invention;

Fig. 4 is a schematic other form of my invention; Figs. 5 and 6 are a side view and top plan,

`respectively., of a detail of the condenser showninFig.4;and...

. Figs. 7 and 8 are details of me', of the condenser plates that are used ix connection with my device.

In Fig. 1, I shov1 a. pair-lof Nicol prismsl 100 i Facaf an electric rather than a magnetic, field to cordiiigly another object of my invention to l 5 gularly with respect to each other that when through will establish' a convenient light 11 and 12, that are spaced a art, across condenser may effect the rotation of the which light can be transmitted) 'from one larized light between the two prisms and the prism to the other. The planes of polarizaanalyzer 12 should have its plane arranged tion of these two prisms are so disposed anso that the polarized beam passing there- 10 no' control action is present, 'the light atlcvel, the intensity of the light being capable tempted to` be transmitted through the pf rariationbotli to reduce and to increase prisms, is dimmed; that is, the plane of po-- it as the field is'rotated.

larization of prism 12 is disp accd by-an Between the two sets of plates of the con-` l 10 angle that is nearlv 90 from the plane of denser 19 are impressed potential differences 75 polarization of prism 11. Y A which vary in accordance with the sound to However, it is wel-l understood that if the be recorded. These potential differences in plane of polarization of the polarized light turn cause corresponding differences in the in -the 'space between these two prisms is roelectric field through which the polarized i. 15 tate'd, then the'eect is as'if one ofthe prisms light must pass, and these differences canse 80 would be rotated; and therefore more light corresponding rotation of the polarized will be passed through the analyzer 12. The light., Therefore, there is a direct functional m2011111? thus transmitted depends llpOIl the relation between the potential di'erencelim.

degree of rotation of the plane of the polarpressed acl-ogs the condenser 19 and the 2o ized light. The greater the rotation tending amount O f light that is permitted to pass 85 to parallel to the polarization with the plane through both prisms 11 and 12 with the re. of analyzer 12, the more light will be passed gulf, that record on 51m 0r Strip 18, which through the, two prisms. follows faithfully the potential diierences on In the present instance I show the source the condenser 19, In' case elements 19 be a 26 of light 3S lam 13 Wlfh its reflector 141 transparent film, this record takes the form 90 which pil'SSS IS ight f o o lonlsvsysfm 15 of variations in density, of the film. In the focusing its rays at a point intermediate the case of sensitized paper strip hat is ordina.-l .two prismsll and .12: ffl' the llt-5h17 PaS- SCS rily opaque, the record takes the form of varihlollgh PHSm 12 1t 1S Converged by a C.YI m' ations in the density of its sensitized surface,- 3Q,- Timmons 15 lhl'ough im Pollini-'o folzlllmg which surface can be utilized asa refiecting 95 f plate or iris 17, and onto a moving sensitized surface to reproduce the soum'is phoglecstrip or film 18. This strip or film 18 can trjcauy I l .the {lual Photograph@ mm: ,0.1' 1t malba a The manner in which sou-nd 'can produce sensitized Strip of Paper If 1t be a Stnl o f variations in potential difierenee across con-- 3,5, paper, tbe record can be formed as a' varidenser 19 will now be described Sound 100 ation in the density of the sensitized surface Waves affect transmitter or microphone' 21 of the Paper Whlch can be Sed s a rct whereby the current fiowing in a circuit con. mg Surface? rather ha? 35 a transmitting nected to the transmitter is correspondingly surface. The lin or strip 18 can be moved Yae This circuit can include he primary i 4o by any appropriato mechanism: which forms eoi122 of an iron cored transformer 2O and a m5 no Part of my resent invenfom source of potential such as the batte 23.; In order to o @ci the rottlon of the Polar' The secondary coil 24 for the transfornr 25 Wod.' hght bewoen' the Prlsms 11 and 12J I can affect the input side ofan amplifier 26. v utilize in this instance-a means for providing This ampler 5S indicated in the present 45, variations in the electric field transversed by instance as an electronic emission device, .no

the polarized light. Preferably this means having an electron -emitting electrode 27 in can. frmed as a {null-*Plate condenser,19 the form of a filament .heated by current, as encased, m an encasmg body ..20 ,ned with Vfrom a battery 28. This electrode, as well some liqind gabs-tance that 1s @Fable of as the anode or plate electrode-29, is enclosed;

5a tlansmlttmg 4hght and .that rovldes a ,me' iiian evacuated vessel."1"heelectronseinitted n.5 (imm whereby the. rotation 0 the Polarized vfrom filaments 27 flow to the late or anode light is obtained. Such .substances are for 29Vbecause this plate or ano is keptA at a, example merrc Potasmm, Odlde or cai" potential positive with respect to filament 27;. bon disulfide'. In Fig. 1, the condenser 19 is This is secured by the nid of an external cib 5.5. ShoWl1- dagrammatic'auy it being under cuit including a heavy inductanoe or im? 12' stood that in act-ual practice the condenser Pedan 30 and Source of potential 3l Such plates shown therein forni a series -of spaces as a battery; which two lemengs 30 and 31 tloughrvhich the-1`ht n 1321553511' other connect the electrodes 27 and 29 externally words, the'condenser 19 is shown as rotated of the amplifying device 25.-. i, y

'^ an about 90.on its vertical axis from its true The electromc emissio-n device ggjslo-; las

f position in order to showl its structure more dud-s a @ntl-o] electr-Oda 32.A This is usually Clearly. It'ShOuld be ill-S0 noted that, the in the form'of av grid interposed between the',

. prism 11 should have its plane of polarizaelectrodes 27 and-29 and serves to control the tion displaced about 45 from the plane of fiow of space current between ilament27 and .te theplates. in condenser 19 inorder that the anode 29.' It has been fond that even minute 13 variations in 'Leonesa 1 i35 across the inputl electrode 27 and 32 of the.

device 26, then a correspondingly variable space current iiow takes place inthe ouput circuit including inductance coil 30 and the battery 31. For this purpose, one terminal of coil 24 is directly connected to. the grid 32; and its other terminal is connected through the negative bias battery 33 to thev filament 27 aube By making the impedance coil 30 large enough so as to have a very high inductance, the potential difference across that coil can made to vary in accordance with the sounds that are impressed upon the microphone 21. This potential difference in tum can be utilized to affect succeeding amplifiers; but since the mode of cascading the amplifiers is now well known, all but the first one 26 isomitted, and the terminals of coil 30 are shown as being directly connected to opposite sides of the condenser 19.

The operation of the systcmas thus described can now he set forth.- The sound afl fe'cting the microphone of transmitter 21 produces variations in potential acrosst-he input electrodes of the amplifier 26. The output prism 12 is converged by the cylindrical lens circuit of this amplifier, which includes the heavy ind'uctance coil 30, is caused to produce variations in electric potentialfacross the plates of the condenser 19. The sourc'e13 passes rays or other forms of radiation lthrough the polarizing prismll, and this plane of polarization is varied m accordance with the potential differences impressed on condenser 19. Therefore, more or less of this light is permitted to pass through the secondary polarizer 12 in accordance with the variations inthe' potential differences nu ressed on condenser 19. The light passing t irough 16 through a small aperture in the iris plate 17 and as the film or strip 18 is passed across that aperture, a photographic record of the sounds are thus produced thereon.

In some instances the condenser 19 may have an inherent resonant period, which vvould interfere with the truthful recording -of the sound waves. In order to obviat'e this,

I indicate a trap circuit across t-hepcoil4 30, including an inductance coil 34 and condenser 35. All currents of a frequency that vcan disturb the operation of condenser 19 are caused to bypass throughthis trap circultnwluch is adjusted so as to have minimum Impedance at that disturbing frequency.

Fig. 2 shows a form of a condenser 19. Ip this case, the casing 2O is shown as cylindrical, forming a space in which the plates can be accommodated. The aum vin which um rotation of the light is obtained can be con-- fined in this casing.4 One'sct of plates is held by stud 36, and the other set 'by stud 37, which extend through the i yalls of the casing 20, and upon which can be formed ap? propriate terminals 38 and 39. Of course j these terminals are appropriately insulated from the casing 20 and from cach other.

In the form of the invention just described,

straight audio frequency effects are produced; that is, the'andio freguency currents are secured by the action o the microphone 21, and these audio frequency variations a'cctthe polarized light. .Howeven it is poible to introduce a. higher fr -u'cncy e'ect into the system, whichhigher requency current can be merely modulated by the audio frequencies secured by the aid of a microphone or its equivalent.

Such a .system is indicated in Fig. 3. As in Fig. 1. there is a source of light 13 with its rcector 14 passing light through a condensing lens 15 converging the rays between the two prisms 11 and 12. In the present instance the condenser structure 40 is shown merely :Ls a two plate device, but it can readily take the form described in connection with F igs.- -1 and 2. ,The polarized light which passes between the lates of lthis condenser 40 is passed throng the Nicols rism 12 and thence through the cylindrica lens 16. P' In this instance the cylindrical lens 16 converges the rays of light through an ob'ecti fying slot 42 provided in the aperture orrning iris 41. The image of the slot 42 in plate 41 -is reduced in size by reducing lens structure 43, and is caused to enter the aperture in a baille plate 44. The image of slot 92 is produced as a very narrow one, directly on the surface of the film or Isensitized strip' 1 45. This film or strip is shown as wound around sprockets 46, 47, 48.,.and 49 and onto' a larger sprocket support 50, which can be driven by any appropriate mechanism.

The advantages of the slot objectifying device, are that the s chronized film orstri 45 need not be place in contactjwith any ins plate such as 41. Instead, merely an image of a comparatively large slot is utilized to' affect the film or strip 44, this image reduced in size so as to form a comparatively thin line 'on the film or strip 45. Therefore,- such serious mechanical annoyances as'di-rt being trapped in ap very narrow slot of'.

opening areobviat The variations in acro the plates of con enser 40 are secured Y in the present instance by modulating radio votiential difference i' or high frequency oscillations, and then uti'- lizing the potential differences produced by' of current, such as pedance such. as resistance 54. An amplifierA variable current' ina path including a source battery 53, and an im- 55 of the type described in connection with Fig. 1 is affected by the'potential differences j existing across the resistance' 54, as by. con- I nectxng its input electrodes respectively to der tov prevent draining o opposite sides of the circuit including elements 53 and 54. 'A stopping condenser 56 i must be interposed in the in ut circuit in orfpthe battery 53. Furthermore, the grid 57 of the device 55 'can be ke t at a potential negative with reis -spect to t e electron emitting electrode 58,

as by a negative bias battery 59 and a high resistance 60, which, are connected between the grid 57' and filament 58- The output circuit of amplifier 55 includes the high indiictance coil 61 and the platebat-- tery 62. The 'potential differences across this' out ut circ-uit are im )ross-ed u )on the in ut A circuit of an oscillator tube 6 that is, 26

This tube has the usual three electrodes;

the plate or anode 65, and control electrode or grid 66. The input and output circuits of this oscillator 63 are coupled together in order to produce oscillation, in a well understood manner. For example, the input circuit includes the inductance coil 67 and .the

1 output ci-rcuit includes indnctance coil 51,

across whichA potential differences are produced by the action of the apparatus. Also connecting the input and output circuit, is a v'ariable condenser 58 by the aid of which the frequency of oscillation can be adjusted, and whereby a capacity coupling between the two circuits is also afforded. Also a fixed stopping condenser 69 canbe utilized between the input electrodes. Across this condenser can be connected the output circuit of the amplifier through .a stopping'condenser 70 and coil 71.

- Since the mode of producing the high Afrequency oscillation forms no art of my present invention, but may be ound in the descriptionsl of theprior art,'further explanation of the action of the oscillator 63mis considered unnecessary; es iecially since other 'equivalent oscillatory s eines can be used.

The mode of operation of this system can now be summarized. Sounds that affect the microphone 52 cause amplified variations in potential across the output circuit of the amplifier 55. These variations in potential are caused to affect the. high frequency ,oscillations setup by the oscillator 63 by aiecting the input circuit thereof. The potential differences secured across the terminals of the coils 51, which is in the output circuit -of the oscillator 63, are impressed upon the condenser 40, and these variations in potential differences cause corresponding variations inthe angle of the plane of polarization of the light passing between prisms 11 and 12. The light the electron' emitting electrode 64,-

'passing through prism .12 is converged -by the" cylindrical lens 16 to form a com aratively wide ray of light through the opening 42 and the plate-41. This wide ray is reduced to a' very narrow'ray by kreducing lens structure 43', and this narrow ray is caused to affect the sensitized film or strip 45 as it moves past the .baille plate 44. v. l

In the forms -ofthe invention just described, the polarized. li ht between risms 11 and 12 is affected by t ie electrostatic field only once in its passage through the electro-l static field. yIt is possible, however, by prof viding a. tortuous course'for thebeam of light,-

.05" wide). in a-block 74 which serves as a` support for the sensitized film or strip 75.

The wide slot is objectified into a very narrow slit by the aid of the cylindrical lens '75x located in a comparatively deep recess 77 in the block 74. The focus of the rays is located at.. v n

the surface of the film 75, as indicated at point 76, whereby a very narrow image of the slot opening 7 3' is provided. The cylindrical lens '75x can be lued, cemented, o'r otherwise fastened into t e bottom of the slot 77 in any appropriate manner. Being located in thebottom of this slot, it prevents such effects as reflection 4and diffraction from the edges of the slot, and the light must pass through the lens 7 5 by refraction, and is focused .as stated before, on the surface of the film or strip 75.

In the present instance, I utilize a condenser structure in connection with reliectors in such a way that the polarized light paing ssl ics

through theprism 11 is caused to 'traverse the electrostatic field a number of times before it finally reaches the` prism 1'2. For this purpose, source 13 passes light through a b ale .13l to prism 11; thence the beam of light passes through another balile 78 to a window 79 in a casing 80. This casing is Huid tight,

and .can 4be filled with a transparent liquid such as heretofore stated that assists in increasing the rotation of the plane of polarization when' the electrostatic field 'is varied.

The window 79 can be formed on one side of f the casing 80 in any appropriate manner.

The light as shown by the dotted line 81 passes through this window and 'between two plates 82 and 83; The plate'82 can be connected to n terminal post 84 that extends externally of thecasing 80. Adjacent the end of the'passage between plates 82 and 8,3, an inclined mirror 85 is provided,.wh ich reflects the beam iis iid

las'

vof light 81 onto another inclined mirror 86.'

The ray of light reflected from, mirror 86 is caused to pass between the plate 83 and an,- other lower plate 8'7. The reflection of .the beam 81 can be multiplied; that is, another set of mirrors 88 and 89 can be utilized, to pass the beam between plates 87 and' 90. Finally the beam passes through window structure 91, similar to the window 79, and

through the prism 12. The multiple rellection ofthe beam 81 can be carried out to any desired further extent.

The baille plates 131 and 78 are'utilized in l i this inst-ance to guide the light from source 13; instead of lenses. However, the result is substantially the same. By passing the beam of light 81 successively between pairs of condenser plates, it can be more effectively controlled, and tl'iercsultant rotation of its plane of polarization is increased. Alternate plates 82 and 87 can be connected electrically totail in in 1, exce t thatthe ray of light passing through the e ectrostatie field is acted upon a. plurality of times instead of only'once.

This provides a greater degree of rotation for the same variations in potential 'dierences across the condenser structure. In Fig. 4, the output impedance is formedby a large resistancelOB instead of a large inductance. Also, the trap circuit includes a variable resistance 104 whereby its eiect can be adjusted.

Iclaim: 4

1. In a system for recording sound, means for producing a beam of polarizer radiation,

means for creating anelectrostatic field for affecting the beam, means in said field for causing the beam to ass a number of times therethrough, an ana yzer in the path of the beam, and sound controlled means for varying said field.

2. In a system for recording sound, means for producing a beam of polarized radiation, means for creating an electrostatic field for affecting the beam, means for successivel causing the beam to pass back and forti through the eld a number of times, an analyzer in the path of the beam, and sound controlled means for varying said eld.

In testimony whereof I have hereunto set my hand.

DELMAR A. WHITSON.

Each block has a series of saw cuts therein which are parallel and spaced apart for the accommodation of the wide parts -of conf denser lates 82, 83, 87, and 90, shown in de igs. 7 and 8. The posts 84 and 92 can be fastened to blocks 93, 931 as by the aid of screws such as 94 and 95.

The fastening screws 94, 95 also passk through appropriate apertures inplates 82, 83, 87, and 90, to hold them in place and also to makeelectrical contact between these plates and the terminals 84 and 92. Bushings such as 98,199 can be placed in the blocks 93, 931 in the oles through which bolts 94,

conducting material to present good contact A 95 pass. These bushings canbe made of good Il' 105 serve at the opposite ends of blocks 84 'f: f I and 90 to fasten them to blocks 93, 92?1 with-l out contacting with any of the lates. In order ,that the light sha be coaned to a beam between the plates as traced by the dotted line 81 in Fig. 4, the end plates 82 l' r..

and are shown as having the ri ht angled extensions 192 and 103. One of sions is shown in detail in Fig. 8.

The reflecting mirrors 85, se, as and bas "Y can be directly supported on the blocks 93,

931 by prviding that block with appropriate slanting. faces, upon which the mirrors can be appropriately attached.

The operation of this system shown in Fig.

4 is substantially the sameas that disclosed eseexten- 

